Forum » General Tuning Discussion » Misfire , deceleration engine stalling

Misfire , deceleration engine stalling

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
102 Views

Hi hope you guys can help. Recently has my car on the dyno and found that there were some things to fix. Long story short replace the OEM crank sensor with a aftermarket VR sensor and new trigger wire. Also changed coils and ignition driver since the tuner burnt one of the IGBT drivers. ECU reads a steady 59 tooth count from 60-2 trigger wheel. Problem is engine has slight misfire during acceleration and during deceleration and gear down it wants to cut out. One thing I haven’t done is check runout on the crank pulley which is a fluidamper with a trigger wheel mounted to it. Any suggestions?

Do you have a tooth log to show us? Wich ecu?

The only log I have shows the tooth count of 59 with no deviation. I don’t have a log showing tooth profile. I am contemplating buying a picoscope. The ECU is Pantera EFI 882C.

Well can you spot where the tooth is missing? You should have a Longer pulse

The ECU does have an Oscillograph. The wave form doesn’t look even. I’m not sure if it’s the software in the ECU cause I have change sensors three times now. It does show a redline where the missing teeth are detected. Only a proper oscilloscope will give a true reading.

What makes you think you have a trigger problem? Normally if you have a trigger problem there will be obvious symptoms such as unstable dwell and erratic RPM, do you have any of these symptoms? Can you attach a screenshot of the oscillograph?

Have you tried getting in touch with Panterra? I havent touched one for years but the manufacturer Lance Nist is very intelligent and used to be the most helpful man around (dont even know if he is still working or retired).

Hey Adam. Lance is still around I bought coils and IGBT’s from him last December. If I had a picoscope I’d be able to determine if there any problem in the electrical system. One thing I noticed today , it wast hard to start a cold engine, I didn’t drive the car just pulled it into the garage, was rough while free revving. Pulled the plugs and they were pitch black. Engine wasn’t hot either. I have pulled out quite a bit fuel from the fuel table. Spark plug gab was 0.6mm from the last dyno session. Got new plugs on order , will get them tomorrow and see what happens either the fuel reduction in Map.

Hey Adam I forgot to answer your questions. The no irratic rpm. During the drive the engine is very stable. I drive it to work the other day and was cruising at 60kmh in 5th didn’t miss a beat, however when slowing down or coming to a stop the engine wants to cut out. I don’t have any problems with dwell either. The logs I have don’t indicate any problems.when I get the new plugs I take the screen shot of the oscillograph.

From your description it doesnt really sound like you have a trigger problem at all - I suspect something more tune related such as transition from over-run fuel cut or the idle ign control.

I think I might have too much fuel and not enough ignition timing. Can that result in misfire?

You may have mentioned this in another thread, but exactly what engine is being discussed?

For a NA engine, 0.6mm plug gap is negligible and I'd be looking at 0.9 to 1.0mm.

It isn't unusual for spark plugs from a run, but cold, engine to be on the sooty side as it is normally a bit rich for better combustion when cold - I assume 'black' meant dry, not wet? You also may be running a grade too cold/hard for the 'plugs to self clean properly?

A bit of a long shot, but any chance the fuel return and/or pressure regulator is restricting the flow back to the fuel tank? Maybe a kink in the line? This can be a problem, especially with uprated pumps, and tends to show most at when there's low engine fuel demand on the system as the return cannot return all the fuel and the pressure backs up in the rail.

Engine is 20v 5cylinder turbo. Spark plugs were black dry. After drives the plugs end up a light grey. Fuel system was perfect on the dyno session even before that and has a constant 3 bar base pressure.

Plugs are NGK BCPR7ES

Finally managed to sort this misfire issue however there’s another problem. Here’s what I found. The coils are ING-1 and these require a dwell target of 3ms. I changed the dwell from 2.5ms to 3 and also the timing so that engine idles at 15degrees. Spark plugs were side gapped and indexed. Results were smooth acceleration no hesitation or misfires. Now for the next problem. On deceleration the engine would cut out. At idle the engine oscillates from 1300-1600rpm. That’s with the throttle slightly cracked open. Throttle body has 85mm plate. I have tried to adjust the idle control and enable close loop idle with the throttle plate closed, with no success. Attached are some pics of the settings, a video of the rpm oscillating and the idle air controller. Hope you guys can help . Thanks.

Attached Files
  • 1530FBF0-636F-474A-8371-4E74A7EC6FE9.jpeg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

  • 6F4CFEFE-87E5-4B16-8539-5B108EE4ADFC.jpeg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

  • ED8F3BA5-125D-426D-B1C8-EC1DF7DC00CF.jpeg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

  • trim.73DAC6B9-320E-48B7-8CAC-6E770B23988F.MOV
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

To confirm that it is a idle valve control problem and not a general tune problem, does the idle oscillate with the idle valve unplugged? In your video it looks kind of like the MAP ign advance table and RPM ign advance table are fighting each other a bit around the idle area.

The GPO-1 table doesnt look right to me. It looks like it converts stepper motor "steps" into Duty cycle? So I would have expected 15% at the top (fully closed for the Bosch valve) increasing to 100% towards the bottom of the table. So 255 steps closed = 15% DC, 0 steps closed =100% DC...

Also, on the idle control page, the setting "max step rate", Im not sure if that converts to frequency but the bosch valves normally like it at about 200Hz.

Yes idle fluctuates with IAC disconnected. GPO1 table is duty cycle based. By what you describe at zero should be 100% and reduce ( maybe 15%) as manifold pressure increases and top out at 15%. Attached some pics clarify the 255 steps. Max step rate is in Hz, I wasn’t aware that the Bosch motor required 200Hz

Attached Files